This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the presently disclosed invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the presently disclosed invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Various methods are used in the recovery of deeply buried heavy oil or bitumen deposits within oil-sands reservoirs. In situ heavy oil or bitumen recovery techniques are applied to indigenous resource that cannot be mined economically because of the depth of the overburden. It is recognized that in situ methods disturb considerably less land and therefore require less land-reclamation activity than mining projects. In general, the focus of in situ heavy oil or bitumen recovery processes is to reduce the viscosity of the heavy oil or bitumen to enable it to be produced from a well and transported by pipeline or other means. One method of reducing the viscosity of the heavy oil or bitumen is to introduce a recovery-aid solvent, such as by reservoir injection, into the heavy oil or bitumen. Such a process may be referred to as a solvent-based recovery process (such as Cyclic Solvent Process, Hot Solvent Process, and Vapor Extraction). A second method of reducing viscosity of the heavy oil or bitumen is to introduce the recovery-aid solvent along with other viscosity reducing agents including but not limited to, steam, hot water or hot gases. Such a process may also be referred to as a solvent-based recovery process (such as Expanding Solvent Steam Assisted Gravity Drainage, Solvent Assisted Steam Assisted Gravity Drainage, Liquid Addition to Steam for Enhanced Recovery, and Solvent Steam Assisted Vapor Extraction).
Upon recovery, the heavy oil/bitumen is generally in the form of an emulsion containing the recovery-aid solvent as well as water. To separate the water from the emulsion, a separation-aid solvent is generally added to facilitate the separation of the water through density and viscosity reduction.
One challenge in any solvent-based recovery process is the accurate determination of the amount (e.g., mass, volume, percentage, and the like) of the recovery-aid solvent that is recovered from the reservoir along with the heavy oil/bitumen. An accurate accounting of the recovery-aid solvent may be beneficial, for example, in maintaining desirable environmental conditions, determining the efficiency of the recovery process, determining the appropriate processing of the emulsion, obtaining regulatory approval to develop a heavy oil/bitumen project, and/or assessing the economic feasibility of a given solvent-based recovery process.
Conventional methods of measurement of recovery-aid solvent rely on gas chromatography (GC), Fourier Transform Infrared spectroscopy (FTIR), thermogravimetry (TG), solvent evaporation, density measurements, or viscosity measurements. Because of inaccuracies and impreciseness of the other methods, GC is the most preferred conventional method. However, the GC method is not accurate because the boiling ranges of the heavy components in the solvent overlap with the light components in the recovered crude. Also, the reliability of the GC process may not be optimal due to the potential for contamination of the GC column by non-eluted heavy oil/bitumen.
As such, there is still a substantial need for an improved system and method for determining the amount of a recovery-aid solvent in the recovery-aid solvent diluted heavy oil/bitumen that is produced from a reservoir.